Author Topic: SaratogaWX Blitzortung build diary.  (Read 10189 times)

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Offline miraculon

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Re: SaratogaWX Blitzortung build diary.
« Reply #25 on: September 26, 2013, 10:14:17 PM »
Ken,

Great that you found the bad solder joint and that took care of the display issue.

I looked at your signal and it seems that you are running big gain, but have a DC offset. There doesn't seem to be anything actually happening. For as much gain as you are running 32x16, you should see a lot of noise at least.

Can you check the signal chain with an o-scope? Something looks amiss...

UPDATE: Upon looking at the schematics, the amplifier board output is AC coupled. Unless the output 2.2uF was in backwards and leaking current, it is probably not originating from the amp board.

Greg H.
« Last Edit: September 27, 2013, 09:41:17 AM by miraculon »


Blitzortung Stations #706 and #1682
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Offline saratogaWX

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Re: SaratogaWX Blitzortung build diary.
« Reply #26 on: September 28, 2013, 12:47:54 AM »
I took the Amp offline, checked all the components against the parts list, and looked over all the solder joints (touched up a few) and everything looks like the picture of the Amplifier board, except that instead of MCP6S91 Low Gain programable amplifiers, I have MCP6S21 PGAs .. I checked the data sheets for the two parts, and the pinouts are identical, and electricals are identical.. the MCP6S21 has -40 to 85C rating while the MCP6S91 has -40 to 125C rating, so I don't think the substitution is important.

I can touch the antenna A and B inputs with a small screwdriver and get some response on the Signal page, but even at high gain settings, nothing seems to appear in regular operation.  Checked the ferrites connections .. they measure about 4 ohms so there is continuity in the connections.  Also tried the Amp 2 connection -- same results.

I don't have an oscilloscope available, so I can't probe the innards to see where the signal may be lost, but it is odd that both channels in the Amp are behaving the same way.

Any more advice???

Puzzled,
Ken
Ken True/Saratoga, CA, USA main site: saratoga-weather.org
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Offline W3DRM

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Re: SaratogaWX Blitzortung build diary.
« Reply #27 on: September 28, 2013, 01:02:17 AM »
Ken, there are pc-based o-scope programs that use the sound card for the inputs. I haven't looked into it myself but that might be something to try in lieu of having a real o'scope. Search for "soundcard oscope" and you'll get quite a few hits.

Here are a couple links you might want to look at:

Hope this helps... I hope to have my system completed early next week. Again, family and other things got in the way of getting it done today and this evening.  :-(

« Last Edit: September 28, 2013, 01:39:56 AM by W3DRM »
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Offline miraculon

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Re: SaratogaWX Blitzortung build diary.
« Reply #28 on: September 28, 2013, 10:41:29 AM »
When I first completed the amp board, I touched the input and looked at the output on the AC scale of my DMM. At big gain you should be able to see output. There is a band-pass filter, so the old "hum" test isn't as valid as it would be with a typical audio amplifier.

Is there an old Walkman or MP3 player that you could get a 10KHz tone recorded on? You could inject this at the input and trace it through the system with a DMM or better, one of the suggested PC scope programs.

Does the DC offset scale with gain? If you turn the gain down to minimum, does the DC offset go closer to zero? That would be a further indication of where the trouble is.

Check that the C15 and C30 electrolytic caps are the correct polarity on the amplifier board. They will leak DC current if they are reversed. Does DC appear at the OUT-A and OUT-B? Assuming you have a meter.

Greg H.





Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
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WU: KMIROGER7
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Offline miraculon

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Re: SaratogaWX Blitzortung build diary.
« Reply #29 on: September 28, 2013, 03:12:56 PM »
The only other possibility that I can think of is that some ADC settings or coefficients in the flash memory are corrupted. I doubt this because it is unlikely that the same issue would be on both channels. It might we worthwhile to try a "reset settings" to clear out the flash memory to defaults. It is a long-shot, but it is an idea to try.

Greg H.



Blitzortung Stations #706 and #1682
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CWOP: CW4114 and KE8DAF-13
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Offline saratogaWX

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Re: SaratogaWX Blitzortung build diary.
« Reply #30 on: September 28, 2013, 08:15:46 PM »
Been offline chasing down ideas you've highlighted above .. thanks again for the continuing ideas.

I decided to acquire an oscilloscope and counter/frequency generator -- living close to several Fry's outlets can make you do crazy things like that.  I found a Tektronix TDS1002B 60Mhz dual channel digital storage scope (discontinued) as one of two at Fry's in Palo Alto and a counter/function generator.  I've now spent more on stuff around the Blitzortung kit than for the kit itself, but it does feel satisfying to have a Tek scope (much better than the monster I'd used back in the '70s).

So, did the DC voltage test with the DMM on the output leads.. Looks like I have about +4.1mV DC on the output, and it does not change with gain (tried 1:1 to 32:32 for gain settings).  The C15 and C30 are in the correct polarity (negative stripe facing the test connector pins, which matches the photo of the board from the doc).

I hooked up the new scope and signal generator .. with 20mV P-P 10KHz input the output scales on amp-A and amp-B as you'd expect from the gain setting.  At 32:32 the 20mV input signal is 2V P-P (1024 gain).

I'll post some scope pictures as soon as I figure out how to capture them :)  Had to find a 256Mb flash drive, update the Tek firmware, and got the two captures (attached) .  CH1 is the output pin, CH2 is the antenna pin.  First image is Amp-A, second is Amp-B

Short story.. looks like the Amplifier(s) are behaving correctly, and amplified signal does pass through from A and B

So what to check out now?

Best regards,
Ken
« Last Edit: September 28, 2013, 09:53:34 PM by saratogaWX »
Ken True/Saratoga, CA, USA main site: saratoga-weather.org
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Offline miraculon

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Re: SaratogaWX Blitzortung build diary.
« Reply #31 on: September 28, 2013, 09:05:29 PM »
Wow, that's a nice scope. I hope that you get good use out of it for many years. The closest Fry's to me is in Indy, but I get to go there every so often.

I think that this exonerates the amplifier completely. The generator and scope was the best way to prove it.

I would shift the focus to the controller board now. Using the schematic and ST Discovery board user manual at http://www.st.com/st-web-ui/static/active/en/resource/technical/document/user_manual/DM00039084.pdf?s_searchtype=keyword I would connect your generator to the amp as before and trace it to the Discovery board pins associated with the ADCs. If it is getting to the ADC pins on the top side of the Discovery board that will be another check.

Also, see the schematic fragment I have attached. Check that there is 1.5V at the center of the voltage divider from 3V to ground. This is the AC 'pseudo-ground' that the signals swing around. The signals on the ADC input pins should be biased to close to this point. The signals in a single-ended analog circuit swing from ground to the supply (more or less) and should be at the 1.5V bias point with no signal.

The 1.5V point is just DC, you won't see signal there. You should see the signals "riding" on top of the 1.5V bias voltage when you feed them in from the generator via the amplifier board.

Were you able to try a re-flash of the ST Micro? You could try that if the hardware checks out.

I hope that you didn't get a bad ST board, but it is possible that there is a problem with the ADC circuits on it.

Good luck and I hope that you can track it down OK.

Greg H.







Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline miraculon

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Re: SaratogaWX Blitzortung build diary.
« Reply #32 on: September 28, 2013, 09:18:05 PM »
Another question:

When you scale the gain up/down, does this change at all?

http://www.blitzortung.org/Scripts_php/php_signal_2.php?station=802&region=3&mode=signal&unit_width=2&unit_height=12

Greg H.



Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline saratogaWX

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Re: SaratogaWX Blitzortung build diary.
« Reply #33 on: September 30, 2013, 02:03:13 PM »
I've been fiddling a bit with the system.. currently have the gain cranked to 32:32 and have the odd disparity between Chan-A v.s Chan-B



With the gain set the same, I'd really expect the output/noise level to be the same .. Should I look for some issue in the Chan-A side?

@Greg:  yes, the php_signal_2.php display does change, but only if I use high gain settings 32:16 or 32:32.  I have re-flashed (using the web interface) the 4.4 Firmware .. no change in behavior.

I'm starting to suspect that there is something amiss in the Amp-A channel...

Here's another question..
I currently have ' Ferrite rod, SKS120N, 120mm, W. Friese' set for the antenna type .. is that correct for the ferrite rods shipped with the default kit of parts?

Best regards,
Ken

Ken True/Saratoga, CA, USA main site: saratoga-weather.org
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Offline W3DRM

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Re: SaratogaWX Blitzortung build diary.
« Reply #34 on: September 30, 2013, 02:47:21 PM »
Ken, what happens when you swap the ferrite inputs to the amplifier board? That should tell you if the problem is in antenna or the amps. If it's the antenna, then the relative waveforms should move to the other amp. If it is the amp then you will see little of no change to the waveforms.

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Re: SaratogaWX Blitzortung build diary.
« Reply #35 on: September 30, 2013, 03:14:37 PM »
Good idea, Don.  Here's the captures before/after swapping the two ferrite antennas:






It looks like A-channel has about 1/4th the gain at 32:32.
Ken True/Saratoga, CA, USA main site: saratoga-weather.org
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Offline W3DRM

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Re: SaratogaWX Blitzortung build diary.
« Reply #36 on: September 30, 2013, 03:34:11 PM »
I'd suspect a problem with the Amp A circuitry. Going all the obvious things;
- Have you checked all of the solder connections for bad or missing solder joints?
- Any solder bridges?
- Since you have a scope do you see any input at the input pins?
- Then, looking at the output pins do you see any increase (amplification) in the signal output?
- Voltage comparisons between the two amps may also help find the problem.

Best of luck...
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Offline SLOweather

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Re: SaratogaWX Blitzortung build diary.
« Reply #37 on: September 30, 2013, 03:49:40 PM »
I've been meaning to mention this for a while. I've had trouble, even on my little VP2 interface board, with SMDs and solder joints. I finally started using a 10x loupe to check them and found some "dry" joints. Some would even work OK 'til the boards were coated, and then fail.

Inspect closely, and reflow if in doubt.

Loupes are available from Digi-Key and Mouser among others, and are cheap. I use the monocle style, but a hand held one like rock hounds and stamp collectors use would be OK.


- Have you checked all of the solder connections for bad or missing solder joints?
- Any solder bridges?

Offline miraculon

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Re: SaratogaWX Blitzortung build diary.
« Reply #38 on: September 30, 2013, 03:53:58 PM »
I thought that everything was hunky-dory with the signal generator and you were able to reach about 2V pk-pk on the amp outputs.

This would tend to lead to the conclusion that the amp channels are OK.

Are you putting the antenna wires directly into the screw terminals? You should solder the magnet wire to a larger stranded wire for the screw terminals.

Also, the insulator on the coil wires isn't the solder-strip type. It needs to be carefully scraped off to be soldered to the wires. Can you measure the continuity at the screw terminals and see the DC resistance of the antennas at the screws? Maybe it isn't making good contact.

Greg H.



Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline W3DRM

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Re: SaratogaWX Blitzortung build diary.
« Reply #39 on: September 30, 2013, 05:13:46 PM »
I thought that everything was hunky-dory with the signal generator and you were able to reach about 2V pk-pk on the amp outputs.

This would tend to lead to the conclusion that the amp channels are OK.

Are you putting the antenna wires directly into the screw terminals? You should solder the magnet wire to a larger stranded wire for the screw terminals.

Also, the insulator on the coil wires isn't the solder-strip type. It needs to be carefully scraped off to be soldered to the wires. Can you measure the continuity at the screw terminals and see the DC resistance of the antennas at the screws? Maybe it isn't making good contact.

Greg H.


Putting my old Field Engineer hat on:

Ken has already switched the antenna wire inputs and the result shows a similar output. Since the problem did not move, the circuitry associated with Channel A (including the wire connections as suggested by Greg H.) has some kind of problem. Ken needs to follow the signal with his scope from the input, through the op-amp stages and all the way until he finds where the signal is getting attenuated or not passed correctly. It could also be on the Controller board.

IDEA: BEFORE tracing signals with the scope and, to further isolate the problem, do the following first:
- Move the shielded cable coming from the Amplifier board to the other RJ45 input on the Controller board. This will help isolate individual channels on the Controller board if the problem is with the controller board itself.

The other thing we haven't eliminated is the cable itself between the amp and controller board.
- Move the cable to the second controller input. If this doesn't doesn't change anything,
- use another cable to eliminate that.

If the problem still exists, you will just have to follow the signals from component to component until you find where it goes bad.

Just be very careful with your scope probe that you don't short-out any adjacent pins.

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Offline Jumpin Joe

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Re: SaratogaWX Blitzortung build diary.
« Reply #40 on: September 30, 2013, 05:53:42 PM »
Having had the same problem as Ken.... I'd check the solder joints, very closely, on the channel that is in question and re-seat the IC's for that channel as well. Once I did both, my problem went away.

Joe

Offline miraculon

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Re: SaratogaWX Blitzortung build diary.
« Reply #41 on: September 30, 2013, 08:17:08 PM »
Ken,

Please oscilloscope probe the pins shown below at the ST-Discovery board with a generator test signal at the amplifier input. They feed the ADCs on the STM processor.

You can ignore channel 3 for now.

You should have about 2/3 (100/147) of the signal as at the amplifier outputs test header, except biased up to 1.5V.
If there is no signal at these Channel1 and Channel2 points, there is a problem on the controller board from the inputs to the Discovery board pins.

Greg H.



Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline saratogaWX

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Re: SaratogaWX Blitzortung build diary.
« Reply #42 on: October 05, 2013, 11:56:43 AM »
Having had the same problem as Ken.... I'd check the solder joints, very closely, on the channel that is in question and re-seat the IC's for that channel as well. Once I did both, my problem went away.

Joe
I decided to trace the signal through the paths on the amp(s) checking corresponding levels when the gain was set to 4:4 for both amps.  I used a bit of clipped-off resistor wire in the probe so I could carefully touch pins on the ICs (including the SMDs) without shorting adjacent pins.

Chan-B wasn't working because Pin 3 on IC6a (the input to the first filter amp) wasn't connected (despite it looking connected)



A re-solder of that connection caused Chan-B to produce the same output as Chan-A for all the gain settings (with a 20mV 10KHz sine input).  So, it looks like the amps are both working now.

With the 120mm ferrite antennas connected, I'm now seeing an odd difference between the two:



One of the ferrites is picking up a repetitive 60Hz signal that is associated with that one ferrite, and the signal moves to the other amp if the connection is swapped between the antennas.  I'm trying to figure out where the signal is coming from, but no luck so far.  I did apply E shielding (foil tape) to the antennas (with a 1/8in gap along the axis), and tied the foils together to the antenna ground pins at the amplifier -- seems to have no effect on the periodic signal.

@Greg:  I think the ADCs are working ok since the Chan-B Amplifier is now working.
@Don: thanks for the suggestions .. I have tried them all, and the 'trace the signal' was the resolving diagnostic test :)

Still slogging through the debug, and I'm building a ball-loop antenna to try out also.

Best regards,
Ken
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Offline miraculon

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Re: SaratogaWX Blitzortung build diary.
« Reply #43 on: October 05, 2013, 12:09:36 PM »
That's great. Looks like you are making progress.

It seemed that when you tested it with the generator it was passing the signal, so I thought that the controller board/ADC was the remaining possibility.

Glad you found it. As you said, on to the antennas...

Quote
One of the ferrites is picking up a repetitive 60Hz signal that is associated with that one ferrite, and the signal moves to the other amp if the connection is swapped between the antennas.  I'm trying to figure out where the signal is coming from, but no luck so far.  I did apply E shielding (foil tape) to the antennas (with a 1/8in gap along the axis), and tied the foils together to the antenna ground pins at the amplifier -- seems to have no effect on the periodic signal.

Do the suspect ferrite's antenna wires have continuity with an ohm-meter? Maybe it is acting like a "wick" and the ground side is open? Is there a solder connection between the ferrite magnet wire and your hookup wire? That magnet wire was a bear to solder to as I recall.

Greg H.

« Last Edit: October 05, 2013, 12:21:44 PM by miraculon »


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Offline Jumpin Joe

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Re: SaratogaWX Blitzortung build diary.
« Reply #44 on: October 05, 2013, 12:34:43 PM »
Having had the same problem as Ken.... I'd check the solder joints, very closely, on the channel that is in question and re-seat the IC's for that channel as well. Once I did both, my problem went away.

Joe
I decided to trace the signal through the paths on the amp(s) checking corresponding levels when the gain was set to 4:4 for both amps.  I used a bit of clipped-off resistor wire in the probe so I could carefully touch pins on the ICs (including the SMDs) without shorting adjacent pins.

Chan-B wasn't working because Pin 3 on IC6a (the input to the first filter amp) wasn't connected (despite it looking connected)



A re-solder of that connection caused Chan-B to produce the same output as Chan-A for all the gain settings (with a 20mV 10KHz sine input).  So, it looks like the amps are both working now.

With the 120mm ferrite antennas connected, I'm now seeing an odd difference between the two:



One of the ferrites is picking up a repetitive 60Hz signal that is associated with that one ferrite, and the signal moves to the other amp if the connection is swapped between the antennas.  I'm trying to figure out where the signal is coming from, but no luck so far.  I did apply E shielding (foil tape) to the antennas (with a 1/8in gap along the axis), and tied the foils together to the antenna ground pins at the amplifier -- seems to have no effect on the periodic signal.

@Greg:  I think the ADCs are working ok since the Chan-B Amplifier is now working.
@Don: thanks for the suggestions .. I have tried them all, and the 'trace the signal' was the resolving diagnostic test :)

Still slogging through the debug, and I'm building a ball-loop antenna to try out also.

Best regards,
Ken

Ken, glad to see you are making progress. I am glad to see you haven't pulled out the sawed off to solve the problem. No doubt, I have less hair now then when I started my kit.

I am ecstatic with the success of my ball antenna. Just finished relocating it to the attic of my garage, another reminder that I'm no kid anymore, to get it away from all noise issues. Immediately, I had to crank down my gain. Another day or two to get the right settings.

Best of luck!

Joe   

Offline W3DRM

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Re: SaratogaWX Blitzortung build diary.
« Reply #45 on: October 05, 2013, 12:39:38 PM »
Ken,

Congrats on finding the bad connection!  =D>

Since the problem moves when you swap the antenna inputs, I wonder if there is some kind of wiring problem with one of the ferrites? Have you ohmed them out to see if they compare in readings? The readings will be quite small. Another thought - have you scoped each of the ferrites (not connected to anything but your scope lead) to see if they both have the same output traces?

It sounds like you are picking up some kind on signal on one of them and not the other.

Keep going, you are certainly getting closer to be operational.

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Offline saratogaWX

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Re: SaratogaWX Blitzortung build diary.
« Reply #46 on: October 05, 2013, 04:57:14 PM »
That's great. Looks like you are making progress.

It seemed that when you tested it with the generator it was passing the signal, so I thought that the controller board/ADC was the remaining possibility.

Glad you found it. As you said, on to the antennas...

Do the suspect ferrite's antenna wires have continuity with an ohm-meter? Maybe it is acting like a "wick" and the ground side is open? Is there a solder connection between the ferrite magnet wire and your hookup wire? That magnet wire was a bear to solder to as I recall.

Greg H.

I checked the continuity of both ferrites to their terminals (3.2Ohms) -- yes, had to carefully scrape the varnish off, tin the wire, then solder it to some Amphenol pins (gold plated) to use for the connections to the antenna block on the amplifier (also shrink-wrapped the connections).

A question:  what does the knot on the lead to the ferrite mean?  Is it the start of the wrap or the return?  Should the knotted wire be used for the signal input or connected to the common ground on the antenna terminals?  Or, does it really matter as long as both ferrites connect the same way (knot to signal or not)?  

I've connected the Controller and Amp with a 50ft shielded Cat-6 cable so I could walk the antenna to various locations.  The interference is stronger towards the kitchen area (even with RE1000 repeater, florescent lights and house phone unplugged, and family room TV/lights off).  Signal is weaker in master bathroom at other end of main all, but still unable to determine where the interference is coming from.  Grrr...

As I rotate the antenna in the horizontal plane, I can see the interference peak on one channel, then the other, so my prior statement about it not moving was incorrect.  The signal is strongest on the ferrite pointing along the long axis of the rod.  Does that mean the longitudinal axis is pointing in the direction of the signal, or is the perpendicular the direction of the signal?

It's been too long since EE school to remember that.   #-o  :oops:  :roll:

Edit: found that answer
Quote
The ferrite rod antenna operates using the high permeability of the ferrite material and in its basic form this may be thought of as "concentrating" the magnetic component of the radio waves. This is brought about by the high permeability μ of the ferrite.

The fact that this RF antenna uses the magnetic component of the radio signals in this way means that the antenna is directive. It operates best only when the magnetic lines of force fall in line with the antenna. This occurs when it is at right angles to the direction of the transmitter. This means that the antenna has a null position where the signal level is at a minimum when the antenna is in line with the direction of the transmitter.
So the perpendicular points to the signal source (and 180 from it).  Search is your friend :)
« Last Edit: October 05, 2013, 05:14:00 PM by saratogaWX »
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Offline miraculon

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Re: SaratogaWX Blitzortung build diary.
« Reply #47 on: October 05, 2013, 05:14:01 PM »
This chart is very helpful. I think that RichoAnd posted it on the main Blitzortung forum.

On the ferrite rod antennas, the pattern is perpendicular to the rod. On electrically small loops the pattern is in the plane of the loop.

I had to make myself a cheat sheet for this (and spent a lot of time looking it up, but Richo's chart is better).

Deep in the Blitzortung PDF, there is a mention of the "knot". The convention is to make that the positive (or signal input for Red). Richo also mentions that it really doesn't matter on the posting Antenna question over there on the main forum.





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Re: SaratogaWX Blitzortung build diary.
« Reply #48 on: October 05, 2013, 07:37:10 PM »
To further define the meaning of "direction sensitivity", are we referring to "magnetic" or "electrical" field? And, when one is trying to find a source of interference, would one rotate the ferrite antenna so it was broadside to this source. For example, if I have a source of interference that is due North of my location would I find it by rotating the ferrite antenna so it pointed towards the north or would I point it so the antenna is broadside (90 degrees) to the source of interference?

Hope I'm making sense here but it will help all of us to correctly orient our ferrite antennas so we can identify sources of interference.

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Re: SaratogaWX Blitzortung build diary.
« Reply #49 on: October 08, 2013, 05:02:13 PM »
I decided to build one of the Ball loop antennas using a 10in solid foam ball from Michaels' craft supply store.  The antennas are shielded by foil tape and consist of 30 turns of 20gauge magnet wire.  I've not noticed much difference in reception from the default 120mm ferrites that Egon sent.  Also tried terminating the antenna leads at the amp end with 100ohm termination resistors.. no change to speak of.



Here's the 60Hz noise I can't seem to locate:



By rotating the ball in the horizontal plane just so I can minimize the noise spikes and crank up the gain to 10:4 currently.  So here's a better look, and you can just see the interference showing up at a minimum.




I'll have to port the antenna/AMP around the house some more to attempt to pinpoint the source of the interference.  Thanks for the education about directionality of both the loop and ferrite antennas -- that is very helpful!

Best regards,
Ken
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